In the use of first and second members rotatable one relative to the other, it is desirable to seal an annular opening between the members to prevent passage of foreign matter through said annular opening. According to the present invention, a seal is used to block passage of foreign matter between the first and second member.
U.S. Pat. No. 3,998,297 which issued on Dec. 21, 1976, to Aono shows a brake assembly having a backing plate and cover plate connected thereto which form a labyrinth barrier to material passing between the backing plate and an associated brake drum. U.S. Pat. Nos. 3,533,491 and 3,463,273 which issued to Svenson & Morrison on Oct. 13, 1970, and Aug. 26, 1969, respectively, show similar embodiments of barriers on brake assemblies.
U.S. Pat. No. 3,438,639 which issued on Apr. 15, 1969, to Paulsen shows embodiments of packing devices for rotating shafts which utilize elastomeric seals to seal annular openings between a shaft and bearing and support housing. U.S. Pat. No. 4,043,620 which issued to Otto on Aug. 23, 1977, shows embodiments of seals similarly used. U.S. Pat. No. 3,687,464 which issued on Aug. 29, 1972, to Jackson et al shows an embodiment of a seal used between surfaces of a shaft and related perpendicular abutment.
For example, in a lift truck, a brake assembly generally has a backing plate connected to an axle housing. A wheel of the lift truck mounts to a hub which is rotatably connected to an axle tube. The hub includes a brake drum portion. Brake shoes controllably ride against the brake drum portion to slow or stop rotation of the wheel relative to the axle tube. The backing plate is provided to prevent foreign matter from entering the drum which can interfere with the operation of brake shoes against the rotating hub. However, because of relative rotation between the backing plate and hub, an "annular opening" is necessarily maintained between the hub and backing plate. During operation of the vehicle, dirt, rock, or water for example, can enter through the annular opening and interfere with brake operation.
Heretofore, metal plates have been connected to one of the backing plate and hub and angularly extended over the other of said members to form a baffle or labyrinth against entry of the foreign matter. This type of solution, however, does not create a positive seal between the two surfaces and dirt and water can still enter the brake assembly, especially in the harsh environment of a work vehicle such as a lift truck.
The present invention is directed to overcoming one or more of the problems as set forth above.